Paint spray gun



June 5, 1962 H. F. BoK ETAL PAINT SPRAY GUN Filed Jan. 4, 19Go )yell/DRM 8M,

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llnited States Patent @t 3,037,709 PAENT SPRAY GUN Hendrik F. Bol: and Edward Bok, both Bankiers Hope En Co., Karperstraat 7, Amsterdam, Netherlands Filed Jan. 4, 1960, Ser. No. 369 7 Claims. (Cl. 239-412) This invention relates to a paint Aspray gun spraying medium discharge control means, wherein the spraying medium for the paint is a hot vapor obtained from liquid.

In conventional paint spray guns which utilize air as a spraying medium, the air-tight valving control of the air discharged from the spray gun does not present `a problem. A small air-leak can be completely neglected, ilrstly -because Iair is a cheap and easily obtained spraying medium and secondly, since air is a cold spraying medium the valving is easily effected. Even in the case of a small leak the leaking air is invisible and has no harmful ettfect upon the surface to be sprayed.

In paint spray guns using a vapor phase obtained by the heating of `a liquid, leakage of the spraying medium is to be avoided as much as possible, since the hot vapor phase is relatively expensive, because obtained by converting a hydrocarbon to vapor under pressure. Furthermore, leakage, especially When the gun is not operating, may result in the escape off a hot Vapor which condenses to liquid and may fall in drops upon the surface being painted.

The valve which is conventionally applied to a v-alving pin in the control of air `discharged from a conventional spray gun cannot readily be used in paint spray guns which utilize hot vapor las ia spraying medium. Even with very expensive packing material leaking of hot vapor, condensed or not, proves unavoidable after some time.

The spraying medium discharge control means, according to the instant invention is characterized by the employment of a bellows which serves as Ia Valve at one end and which at the other or limi-ting end enjoys a pressure tight connection to Ithe housing of the spray gun.

Conventionally, to obtain an oblong paint jet with the help of the spr-ay gun, jets of spraying medium are used, which are discharged from the sides of the spraying head of the gun and converge upon a paint discharge cone. This soecalled at spray can be adjusted in conventional spray guns by placing an 'adjustable flow-resistance in the supply conduit of the spraying medium to the flatspray channels.

According to this invention, the valving end of the bellows is employed to close selectively the spraying medium supply conduits.

ln conventional or air spray guns -a trigger mechanism is employed 4to actuate a valving pin in the tairsupply conduit and simultaneously actuate a valving pin in the paint discharge conduit. Normally, air is iirst discharged and, sequential-ly paint is discharged. For design purposes, the air control means are usually located below the pain-t control means within the handle of the spray gun, and the air valving pin has to be moved by the trigger mechanism over a relatively large distance. A compression spring is employed conventionally to urge the sealing portion of the valving pin into the air discharge conduit when the valving pin is released by the trigger mechanism. When the valving pin yis thus in the position of completely or substantially completely closing the yair discharge conduit, the compression spring exerts the smallest force on the valving pin, so that in connection with this small spring force, the packing mass may only press lightly against the sealing portion of the valving pin. The application of this type of conventional valving djg Patented .lune 5, 1962 2 for hot vapor spraying medium is, ticable.

When using .a paint spray medium in hot condition in the spray gun, according .to .the instant invention, the spraying medium is passed straight from the supply tubing into the spraying head of the gun and not through the handle. Further, the spraying Ihead is connected to and insulated `from the back of the spray gun by a stainless steel pin. This is to prevent the handle and trigger mechanism from becoming too hot.

In the instant spraying head there is also located the control or valving pin -for the spraying medium. The long way the control-pin for the spraying medium has to t-ravel for discharge in conventional spray guns makes it practically impossible to .apply ia bellows device with bel-lows of the beforementioned great length in a small spraying head.

Il`he spray gun according to the instant invention is further characterized by the fact that the valving pin which controls the discharge of the spraying medium is subjected only to a pressing sealing or closing force by the trigger mechanism, and not to a conventional pulling or `opening force intended to'rnove the valving pin from the liow opening. The valving pin is thus moved by spring force as well as by pressure of the spraying rnediurn bearing against the valving pin which needs travel only a short distance. A further characteristic of the instant spray gun discharge control means is that where a force is required to open the valving pin in the spraying medium discharge conduit, said force is obtained by the service pressure of the spraying medium bearing on the Iresi-lient bellows surface, whether or not increased by the Iforce of -a spring device, and fby a -force derived from the service pressure on the sealing surface of the sealing portion of the valving pin. This resulting force moves the valving pin to `open position from the spraying medium discharge conduit when the trigger mechanism is drawn by the hand of the operator against the handle of the spray gun.

A 'further characteristic of the instant invention is that the bellows surface on which the opening force of the spraying medium is exerted, is larger than the sealing portion ofthe valving pin for the spraying medium. This rneans Ian opening force derives from the difference of service pressure of the spraying medium in these two areas.

For a minimum opening of the spraying medium discharge conduit, the reverse force-produced by the service pressure of the spraying medium bearing on the sealing portion of the valving pin-is changed into a force promoting the opening action. Bellows constructions normally used may be compressed over a certain distance, but may not be pulled longitudinally. When the sealing portion of the valving pin lies against the spraying medium discharge conduit, the bellows are practically relaxed or at rest. As soon as the trigger mechanism releases the valving pin, there will at first be no, or practically no, compression-spring force in the bellows, and, in certain cases, even a small pull spring force. Now the resulting force of the spraying medium is sulicient to make the traveling of the sealing device over the first portion of its way possible, after which the above described reverse force bearing initially on the sealing portion of the valving pin changes into a force of the same direction, so that an increase in the spring force of the bellows can easily be overcome.

The auxiliary valving pin of the flat spray discharge conduit is also regulated by the instant bellows oonstruction.

A further characteristic of the instant invention is that only one bellows construction is used for operating of therefore, impracthe valving pin for the round spray discharge conduit and for the llat spray discharge conduit.

A successful embodiment of the instant control means implies that under the vforce of -a compression spring the auxiliary valving pin bears on the flat-spray discharge conduit. However, due to contraction of the bellows under the above described force, this spring force on the auxiliary valving pin is decreased, after which the auxiliary valving pin is `drawn from the flat spray discharge conduit by means of its link with the bellows. Thus is provided the capability of operating two valving pins by means of one bellows construction, one of said valving pins being movable with respect to said other valving pin over a small distance under the influence of a spring force, without moving said other valving pin. This makes it possible, if desired, to ensure a proper closing of the flat spray discharge conduit during operation by means of the auxiliary valving pin.

A further characteristic of the instant invention is that the force on the valving pin in the ilat spray discharge conduit is realized by means of a spring construction, which spring exerts an opening force on the said valving pin and which opening force, supplements initially that force obtained from the bellows construction.

In conventional paint spray guns the at-spray radjustment is rather fixed and does not respond to the position of the trigger mechanism. If the trigger is moved, then near maximum discharge of the spraying medium is eiected, after which the paint is discharged.

Thus, in the iirst portion of the way traveled by the trigger mechanism in conventional guns the flat-spray valving pin is thus completely or partly open, depending on the previous adjustment of the flat-spray valving pin. In conventional spraying heads the flat-spray discharge orifices are large with respect to the round-spray discharge orifices located round the paint discharge oriiice and they achieve near maximum discharge of spraying medium, also, during first portion of the way traveled by the trigger mechanism.

When using an expensive spraying medium the quantity of spraying medium discharged cannot be ignored from the viewpoint of total operating costs of the paint spray gun, especially When the spraying operation is very discontinuous.

The spray gun manufactured according to the instant invention, has the characteristic that over the rst portion of the trigger movement by the hand of the operator, the discharge of the spraying medium is possible solely through round spray orices in the spray head, thereafter and nearly simultaneously with paint discharge--discharge of the spraying medium may or may not take place through the ilat spray oriices in the spraying head.

A further characteristic of the spray gun constructed according to the instant invention is that, with the trigger normally moved backward, the moment when the spraying medium begins to flow through the flat spray orifices can be adjusted with respect to the moment when the paint discharge is released.

A further characteristic of the invention is that, when in 4a certain position of the trigger only a very small paint discharge is possible, at the same time also a proportionately smaller ow of spraying medium takes place through the flat spray oriiices.

A further characteristic of `the invention is that a stud pin, which is connected with and may rest against the two valving pins for the ilat and round spray, is passed through the trigger device and then nds an adjustable stop in the handle of the gun, which stop controls the way to be traveled to the trigger mechanism; thus also the range of the two valving pins for the spraying medium is adjustable. Further, this stud-pin is surrounded by a press spring, which at one end lies against the said stop in the handle and at the other end presses via the contact surface of a guide tube against the trigger device, so that when the trigger is no longer pressed in by the hand of the operator, the at spray and round spray discharge conduits for the spraying medium will be closed. Also, according to the instant invention, this stud pin rests against a middle-piece, which lies between the press spring and said adjustable stop; and is passed through the trigger mechanism to serve as a stop for the valving pins for the flat and round spray discharge conduits. And also the said press spring exerts a spring force for the auxiliary valving of the ilat spray discharge conduit and possibly also for the round spray discharge conduit; all this force being exerted in such a way that sufficient locking of the adjustable stop is obtained.

Valving of paint discharge and valving of spraying medium discharge are permitted by squeezing of the trigger mechanism, the spraying medium valving pin thus being released prior to pulling of the paint discharge pin. In order to meet the manufacturing tolerances a longitudinally adjustable stop for the paint needle may be applied to ensure proper performance of the gun. Needless to say, the adjustable stop abutting the trigger stud pin may be adjusted cooperably with the adjustable stop for the paint spray needle.

The instant invention is described below with the help of the attached drawing, wherein the FIGURE is a side view, partially in longitudinal section, of a spraygun according to the invention.

In the FIGURE a spraygun, constructed according to the invention is shown. Upon handle 2 spraygun head 1 is attached with the help of insulating pin connector 3 made of stainless steel or the like. Pin connector 3 provides the required heat insulation between spray head 1 and handle 2. Trigger mechanism 4 pivoted at 5 in handle 2 is squeezable by the operator towards handle 2. Cap 6, from which the spraying medium is discharged, is screwed pressure tight onto spraygun head 1 and against paint nozzle 7 with the help of sealing ring 3.

To spraygun head 1 flexible tubing (not illustrated) for the spraying medium is connected via the screwpieces 9 and 10, whereby through the interior channel of screwpiece 9 spraying medium vapor can enter the spraygun head chamber 11. Via the interior channel of screwpiece 10 unexpended spraying medium vapor or a mixture of unexpended vapor and condensed liquid can escape via a returning tube (not illustrated) to a condenser. This return circulation enables a warming of the spraygun head before paint spraying. When paint spraying is started the spraying medium vapor issuing from spray head 1 is invisible and dry and preheats discharged paint to a certain extent. Paint flows simultaneously through externally attached tubing (not illustrated) and into compartment 12 and its discharge is regulated by paint valving pin 45.

In spray head 1 also valving device 13 is attached in a pressure tight manner. Onto Teon or like sealing cone 15 is clamped a valving pin 14. In the front of valving pin 14 flat spray auxiliary valving pin 16 with the guide piece 17 is longitudinally movably seated. Leading edge 18 of round spray valving pin 14 and an inner contacting surface of auxiliary valving pin 16 operate a linking mechanism between the round valving spray pin 14 and the at spray auxiliary valving pin 16. When the spray gun is out of service the auxiliary valving pin 16 rests under the pressure of the compression spring 23 against seat 24 of the flat spray discharge channel 22.

A number of round spray discharge channels 25 located in paint nozzle 7 lead to ring-shaped channel 44 for round spray discharge of the spraying medium, said channel 44 being located between cap 6 and paint nozzle 7.

Flat spray channel 22 is connected via channel 26 with chamber 27 which chamber is connected in turn to the atmosphere through at spray channels 29 for discharge of the spraying medium from the nozzle 7.

Bellows construction 30 is soldered onto round spray valving pin 14 in a pressure tight relationship, said bellows having on its limiting end a lpressure tight connection to the screwpiece 31. Onto valving pinY 14 limiting end the stud 32 of insulating material is attached.

To ensure longitudinal guidance of valving pin 14, exterior screwpiece 31 has annular, extended guidance surface 41, guided by an interior channel in the spray gun housing. End guide ring 42, which is forced around the back part of screwpiece 31 gives additional vertical guidance to the round spray valving pin 14. The trigger mechanism 4 rests during nonservice against stud 32.

The stud pin 33 is positioned apart from the valving pin 14 by means of stud 32.

Against inner contact surface 34 of trigger mechanism 4 rests guide bushing 35 under the pressure of the compression spring 36. The guide bushing 35 slides horizontally in drilled hole 37 of the handle 2 and is thus sufliciently guided longitudinally. In drilled hole 37 also slides middle piece 38. Middle piece 38 abuts stud screw 39 which moves adjustably in screwpiece 40, attached to handle 2. Stud screw 39 provides an adjustable stop for the studpin 33 in its lengthwise direction. The force exerted by the compression spring 36 on the middle piece 38 ensures suicient securing of the stud screw 39 for the adjustable stop positions.

Operation of the spray gun is as follows: In rest, with the trigger mechanism 4 urged against stud 32 by compression spring 36, round spray conduit sealing cone 15 and at spray auxiliary valving pin 16 are pressed against their respective seats by spring 36. Bellows 30 are then almost relaxed. With the help of the stud screw 39 such an adjustment is made that the flat spray discharge conduit 22 remains closed when the trigger mechanism 4 rests against stud 32. When the trigger mechanism is now moved backward, the spring urged force of this trigger 4 on valving pin 14 is removed. In the chamber 11 vapor phase ispresent with pressure on the bellows surface 30 as Well as on the sealing construction of cone 15. This difference in surface areas results in a greater force on pin 14, which as a result draws the cone 15 from its seat 19. This is with the help of the force exerted by the spring 23. As soon as the passage for the spray medium via round spray discharge conduit 20 is somewhat released, the counteracting force decreases owing to the pressure of the vapor phase in the channel 20 on cone 1S. When this cone moves further away from the seat 19 the counteracting force disappears altogether and is then reversed into a force of the same direction. This combined force will suice to overcome the increasing resilience of the bellows 30 inclusive of the possibly occurring shearing stresses in the linking system.

Valving pin 14 will, as a result of the combined force exerted, immediately follow trigger 4 direction, whereby it will move longitudinally until studpin 33 comes to rest against the contact surface 43 of the middle piece 38, thus preventing further longitudinal motion of valving pin 14.

From compartment 11 spraying medium vapor may liow into the atmosphere via round spray channel 20', the ring-shaped channel 21, the channels 25 present in the paint nozzle 7 and the ring-shaped channel 44 between the paint nozzle 7 and the cover 6.

As the trigger mechanism 4 is thus moved backward over a certain distance it has also moved the paint needle 45 by means of a stop 46 on the needle; the motion of needle 4-5 resulting in a discharge of paint through the paint chamber 12 and paint nozzle 7; the rate of dis: charge depending on the position of the trigger. In this way a round-spray mist of the paint is discharged.

Stud screw 39 limits longitudinal movement of the studpin 33 and corresponding self-actuating movement of valving pin 14. As valving pin cone 15 moves away from contact surface 19 closing pressure upon auxiliary valving pin 16 is eliminated. Fla-t spray auxiliary valving in pin 16 is moved from its seat 24. This results in a How of the vapor from compartment 11 into the atmosphere via conduit 20,

conduit 22, conduit 27 and ilat spray conduits 28 and 29 for the spray medium, whereby discharged spraying medium acts on the paint cone in such a way that an oblong spray area for the paint is obtained.

Externally adjustable stop 47 for paint needle 45 provides for regulating paint discharge simultaneously with paint spraying medium discharge. Y

It will be clear that instant spraying medium discharge control means can also be executed in many different ways and also different type of attachment of the spraying head to the housing may be effected without departing from the spirit and scope of invention as dened in the sub-joined claims.

We claim:

l. In a spray gun of the type used for spraying liquid with vapor spraying medium and embodying a spraying medium supply conduit the improvement comprising a single bellows supported adjacent said supply conduit with one valving end directly valving said conduit, according as pressure of said spraying medium varies and another end txedly mounted in the body of the gun; a pin tixed -to said valving end of said bellows and extensible through said bellows; and a trigger mechanism pivoted in said spray gun and urged to abutment with said pin during non-spray operation and pivotable away from said pin to permit spraying medium pressure to open said valving end and thus said supply conduit during spray operation.

2. A means for controlling the discharge of spraying medium in a paint spray gun comprising a bellows having a valving end selectively valving a spraying medium supply conduit, a spray gun trigger mechanism independently pivoted in said spray gun against said bellows during non-spray operation and pivotable away Erom said bellows during spray operation; and an auxiliary valving pin remoVably seated in said valving end of said bellows and engaging at its other end an auxiliary spraying medium supply conduit and said bellows being seated in pressure tight connection between said auxiliary valving pin and the housing of said spray gun.

3. A means for controlling discharge of spraying medium in a paint spray gun having round spray and at Spray supply conduits, comprising a bellows having a Ivalving end directly valving said round spray supply conduit, an auxiliary valving pin removably seated in said valving end of said bellows and selectively valving said at spray supply conduit, said bellows being seated in pressure tight connection between said lauxiliary |valving pin and the housing of said spray gun, a trigger mechanism pivoted in said spray gun abutting said bellows during non-spray operation and pivotable away from said bellows during spray operation.

4. A means for cont-rolling discharge of spraying medium in a spray gun housing of the type embodying round spray and flat spray conduits, comprising a bellows having a valving end selectively valving a spraying medium round spray supply conduit, an auxiliary valving pin removably seated in said valving end of said bellows and selectively valving said at spray supply conduit, said bellows being seated in pressure tight relationship between said auxiliary Valving pin and said housing of said spray gun, a trigger mechanism pivoted in said spray gun against said -bellows during non-spray operation so as to compress and urge said valving end and said auxiliary valving pin respectively against said round spray and said ilat spray conduits and being pivotable away .from said bellows during spray operation; flat spray regulating means mounted in said housing as a limi-t to longitudinal movement of said trigger mechanism and thus said auxiliary valving pin; said bellows when not compressed by said trigger mechanism being responsive to spraying medium pressure and thereby urged away `from said conduits.

5. A means for controlling discharge of spraying medium in a paint spray gun housing as in claim 4, wherein said auxiliary valving pin is spring urged and positioned to exert together with said spraying medium an opening pressure upon said bellows.

6. A paint spray gun control device as in claim 4, including longitudinally adjustable stud pin means removably resting in a handle of said spray gun, extending through said trigger and engageable with said bellows.

7. A paint spray gun device as in claim 6, including spring means surrounding said stud pin intermediate said trigger mechanism and said handle of said gun.

UNITED STATES PATENTS Levine Aug. 2, 1932 Seizer Jan. 8,` 1935 Peeps July 21, 1959 Peeps Sept. 15, 1959 Peeps Jan. 31, 1961 

